hw/intc/loongarch_pch: Modify name of some registers

hw/intc/loongarch_pch: Modify name of some registers

For some registers with width 8 bytes, its name is something like
PCH_PIC_INT_ID_LO and PCH_PIC_INT_ID_HI. From hardware manual,
register name is PCH_PIC_INT_ID instead. Here name PCH_PIC_INT_ID
is used, and PCH_PIC_INT_ID + 4 is used for PCH_PIC_INT_ID_HI.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Clement Mathieu--Drif <clement.mathieu--drif@eviden.com>
Reviewed-by: Song Gao <gaosong@loongson.cn>
Message-Id: <20250507023148.1877287-2-maobibo@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>